Patent

1. A cross-neutralizing monoclonal antibody that comprises an antigen-binding site and specifically recognizes a cross-reactive epitope of the lipopolysaccharide (LPS) antigen structure of Klebsiella pneumoniae , which is an O3b epitope, cross-reacting with an O3a epitope, wherein said antigen binding site comprises an antibody heavy chain variable region (VH), which comprises VH-CDR1 to VH-CDR3 sequences, and an antibody light chain variable region (VL), which comprises VL-CDR1 to VL-CDR3 sequences, said antibody:

A)

is an antibody comprising

a) VH-CDR1 consisting of the amino acid sequence SEQ ID NO:44; and

b) VH-CDR2 consisting of the amino acid sequence SEQ ID NO:45; and

c) VH-CDR3 consisting of the amino acid sequence of SEQ ID NO:46; and

d) VL-CDR1 consisting of the amino acid sequence SEQ ID NO:56; and

e) VL-CDR2 consisting of the amino acid sequence SEQ ID NO:57; and

f) VL-CDR3 consisting of the amino acid sequence of SEQ ID NO:58; or

B) is a functionally active variant antibody of the foregoing, wherein the functionally active variant antibody specifically recognizes said cross-reactive epitope, and comprises

a) the VH-CDR1 sequence SEQ ID NO:75; and

b) the VH-CDR2 sequence SEQ ID NO:76; and

c) the VH-CDR3 sequence SEQ ID NO:77; and

d) the VL-CDR1 sequence SEQ ID NO:78; and

e) the VL-CDR2 sequence SEQ ID NO:57; and

f) the VL-CDR3 sequence SEQ ID NO:79, wherein CDR sequences are according to IMGT.

2. The antibody of claim 1 , which comprises

a) a VH consisting of the amino acid sequence which is any one of SEQ ID NO:11, 68, 69, or 70; and

b) a VL consisting of the amino acid sequence SEQ ID NO:16.

3. The antibody of claim 1 , wherein

a) the O3b epitope is incorporated in the LPS O3b antigen of Klebsiella pneumoniae comprising the structure of Formula (I), including one or more O3b antigen trimannose homopolymer repeating units, wherein Formula (I) is:

MeP→3)-α-D-Manp-(1→2)-α-D-Manp-(1→3)-α-D-Manp-(1→[3)-α-D-Manp-(1→2)-α-D-Manp-(1→3)-α-D-Manp-(1→] n ;

b) the O3a epitope is incorporated in the LPS O3a antigen of Klebsiella pneumoniae comprising the structure of Formula (II), including one or more O3a antigen tetramannose homopolymer repeating units, wherein Formula (II) is:

MeP→3)-α-D-Manp-(1→2)-α-D-Manp-(1→2)-α-D-Manp-(1→3)-α-D-Manp-(1→[3)-α-D-Manp-(1→2)-α-D-Manp-(1→2)-α-D-Manp-(1→3)-α-D-Manp-(1→] n ;

and

c) the O3 epitope is incorporated in the LPS O3 antigen of Klebsiella pneumoniae comprising the structure of Formula (III), including one or more O3 antigen pentamannose homopolymer repeating units, wherein Formula (III) is:

MeP→3)-α-D-Manp-(1→2)-α-D-Manp-(1→2)-α-D-Manp-(1→2)-α-D-Manp-(1→3)-α-D-Manp-(1→[3)-α-D-Manp-(1→2)-α-D-Manp-(1→2)-α-D-Manp-(1→2)-α-D-Manp-(1→3)-α-D-Manp-(1→] n

wherein

MeP is methyl phosphate; and

n is 0-50.

4. The antibody of claim 1 , which has an affinity to bind the O3a epitope with a K D of less than 10 −6 M as determined by biolayer interferometry for bivalent binding.

5. The antibody of claim 1 , which is neutralizing endotoxin of Klebsiella pneumoniae strains expressing LPS molecules comprising any of the O3b, O3a, or O3 epitopes.

6. The antibody of claim 1 , which is any one of a full-length antibody, an antibody fragment thereof, or a fusion protein, each comprising at least VH and VL antibody domains incorporating a binding site recognizing the cross-reactive epitope.

7. The antibody of claim 1 , which is of human origin, or an affinity matured variant thereof.

8. The antibody of claim 1 , for use in treating a subject at risk of or suffering from K. pneumonia infection or colonization to limit the infection in the subject or to ameliorate a disease condition resulting from said infection.

9. A pharmaceutical preparation comprising the antibody of claim 1 , and a pharmaceutically acceptable carrier or excipient in a parenteral formulation.

10. An isolated nucleic acid encoding the antibody of claim 1 .

11. An expression cassette or a plasmid comprising a coding sequence to express a proteinaceous construct comprising a VH and/or VL of the antibody of claim 1 .

12. A host cell comprising the expression cassette or a plasmid of claim 11 .

13. A method of producing the antibody of claim 1 , wherein a host cell comprising an expression cassette or a plasmid comprising a coding sequence to express a proteinaceous construct comprising a VH and/or VL of said antibody is cultivated or maintained under conditions to produce said antibody.

14. The antibody of claim 1 , which comprises

A

a) a VH consisting of the amino acid sequence which SEQ ID NO:14; and

b) a VL consisting of the amino acid sequence SEQ ID NO:19; or

B

a) a VH consisting of the amino acid sequence which SEQ ID NO:15; and

b) a VL consisting of the amino acid sequence SEQ ID NO:20.

15. The antibody of claim 4 , which has an affinity to bind the O3a epitope with a K D of less than 10 −7 M as determined by biolayer interferometry for bivalent binding.

16. The antibody of claim 7 , wherein the antibody is a non-naturally occurring antibody which comprises an artificial amino acid sequence.

17. The antibody of claim 16 , wherein the antibody is an IgA antibody or an IgA to IgG isotype switch variant thereof.

18. The antibody of claim 8 , for treatment or prophylaxis of any of primary and secondary bacteremia, pneumonia, urinary tract infection, liver abscess, peritonitis, or meningitis.

19. The antibody of claim 18 , wherein the subject is an immunocompromised or immunosuppressed patient, or a contact thereof.